The present invention relates to an improved crutch structure, wherein the fork support is formed with a central reinforcing rib for increasing the bending-resistant strength of the fork support. The reinforcing rib and the adjacent wall of the fork support define a recess, whereby after the fork support is molded the recess can serve as a standard face for the processing procedure so that when punching holes on the fork support, no deflection will take place. The fork support and fixing tube are inserted in through holes of the sleeve member so that the waste chips and water produced when processing the fork support can be easily removed. The through hole of the sleeve member for receiving the fixing tube is formed with an annular groove which provides a resilient clamping effect. The end of the adjusting tube is fitted with a tube plug one end of which is cut into several equal sections for providing resilient clamping effect, so that the adjusting tube is firmly supported at two points without loosening or swinging, and when the adjusting tube is installed into the fixing tube, the fastening member of the adjusting tube is guided and compressed by an arched face of the sleeve member to facilitate the installation of the adjusting tube into the fixing tube. Conventional crutch structure is constructed as shown in FIG. 1, comprising an armpit section 11, a fork support 12, a grip 13, a fixing tube 14, a sleeve member 15 and an adjusting tube 16, wherein the relationship between the fixing tube 14, sleeve member 15 and the adjusting tube 16 is as shown in FIGS. 2 and 3. The cross-section of the fixing tube 14 and the fork support 12 is shown by A--A sectional view, wherein the fixing tube 14 has a substantially circular cross-section and two lateral projections. The top face of the projection is arched for closely abutting against the fork support 12. The fork support 12 and the fixing tube 14 is locked together by rivets 21. The fixing tube 14 is inserted into the sleeve member 15 while the fork support 12 is not inserted thereinto. An end plug 121 is fitted into each end of the fork support 12. A resilient fastening member 161 is disposed at the top end of the adjusting tube 16, whereby when the adjusting tube 16 is inserted through a through hole of the sleeve member 15 into the fixing tube 14, the fastening member 161 is aligned with the fixing holes 141 punched on the wall of the fixing tube to achieve an extensibly adjusting effect. The outer diameter of the adjusting tube 16 corresponding to the inner diameter of the sleeve member 15, allowing the adjusting tube 16 to easily slide therewithin, while the inner diameter of the fixing tube 14 is slightly larger than the outer diameter of the adjusting tube 16 so as to avoid the damage thereof due to the friction therebetween. Further referring to FIG. 4, the grip 13 is formed by a central shaft rod 131 and an outer sponge sleeve 132. Two ends of the shaft rod 131 are arch-shaped corresponding to the fork support 12. After the shaft rod 131 is fitted between the fork support 12, a screw 133 is extended therethrough to secure with a butterflynut 134.
Several shortcomings exist in the above arrangement as follows:
1. After the fork support 12 is bent into the necessary shape, the same must be punched with multiple holes (as shown by the holes 0, P, Q, etc. of FIG. 8). Because the fork support has circular cross-section and is likely to roll as shown in FIG. 6, the fork support 12 can be hardly stably secured on a standard surface so that when punching the holes thereon, the holes often are not located in the same central line. Therefore, the installation often cannot be accurately performed and revision or further processing is required for completing the installation. As a result, the time and labor are wasted.
2. As shown in FIG. 2, the arched faces of the projections of the fixing tube 14 abut against the wall of the fork support 12 and the fixing tube 14 is secured with the fork support 12 by rivet 21. However, the test reveals that when the crutch is vertically placed on the ground and suffers a force at the armpit section 11, the crutch will be bent at a portion E and broken at the rivet position as shown in FIG. 8 and photogragh 1.
3. On the other hand, when the crutch is placed at a 45 degrees inclined position with the armpit section 11 fixed, in case a force is exerted on the grip 13, the crutch will be distorted and broken at the hole R of the fork support 12 near the grip 13 as shown in FIG. 9 and photogragh 2.
4. The fork support 12 is not inserted into the sleeve member 15 and the ends of the fork support 12 are plugged with end plugs 121 so that the waste chips and water produced when processing the fork support 12 cannot be removed therefrom and affect the quality of the crutch or corride the inner wall of the fork support 12 and thus the safety of the user cannot be ensured.
5. The shaft rod 131 of the grip 13 has a small long central hole. When extending the screw 133 through the fixing hole of the fork support 12 and the long central hole of the shaft rod, it is difficult to align these two holes. Moreover, the central hole of the shaft rod is apt to disformed by external force and often needs to be redrilled before installation.
6. The conventional crutch cannot provide any warning or locating effect at night so that the safety of the crutch-user cannot be ensured at night or the user cannot easily locate the crutch in a dark place.
7. Bacause the inner diameter of the fixing tube 12 is slightly larger than the outer diameter of the adjusting tube 16, a gap exists therebetween and the adjusting tube 16 cannot closely slide within the fixing tube 12 without swinging. This shortens the using life of the adjusting tube 16 and the user is in danger of falling. Moreover, although the adjusting tube 16 is closely fitted within the sleeve member 15, a long period of abrasion therebetween will make the clearance increased and cause a loosening condition.